Without question grill blocking helps fuel economy and passenger comfort when it's cold out. I fully block the lower grill and leave the upper completely open as that's where the inverter coolant radiator is and cooler is better for electronics. I'm monitoring ICE coolant temp thanks to "Torque" because I sure don't want to hurt this fantastic PIP machine. A couple of days ago I made a 120 mile round trip, through hilly southern Kentucky with outside temperatures in the upper 50's. On the outbound leg I saw coolant temp hit 199 so at the "destination" I removed the grill blocking. On the return trip with a fully open grill the peak coolant temp was 198. Today it's back down to the low 30s, I just put the grill block back & I'm thinking I removed it prematurely. With that background I ask: When do you remove grill blocking?
The rule of thumb has been when the daytime high hits the 50's. Benefit comes mostly from when the temperatures are below freezing. Sadly, that's been quite useful this particular winter. We've seen lots of days in the negatives.
in your particular area, grille blocking is probably not that effective. and temps swinging back and forth in the 40's and 50's make it diificult due to the pain of constant re applicarion. this is where active shutters would be useful.
I guess I didn't ask the right question(s)! How high can the coolant temperature be allowed to climb? Certainly boiling coolant is too hot but that won't happen till over 212f. Or another good question is: at what temperature is the thermostat fully open? I rather doubt that my car has ever had the thermostat fully open, which is why I've said my removing the grill block was "premature". A safe upper limit would have the thermostat fully open yet short of boiling.
Depending on the mixture of water to antifreeze, the boiling point would be over 212F. It's probably closer to 230F in the factory setup. I've seen posters here leave the grill block on above 60F. A Scangauge/Torque app would display the coolant temperature if you're worried.
Yes, I have "Torque" running on a dedicated tablet & that's how I would decide it's time to remove the grill block. But what am I looking for?
Coolant temperature constantly over 200F would be an issue for me. Mine stays between 180F and 190F when it's warmed up but the engine hasn't run since early December as all of my miles have been in EV.
What does "constantly over 200" mean? Since I live in Kentucky, wherever I drive I'm either climbing or descending so the coolant temp is continuously changing. On my last trip I saw a peak of 199 & decided to remove the grill block, but right after the peak it fell to 188 on the next downgrade. I'm now thinking I should wait for a peak of 205 and hope the cold weather is over so I'm not reinstalling in a day or 2 as just happened.
I'm doing 50 % of lower between 5 and 10 centigrade. If temps are consistently under 5 I'll go to 100% block. I never block upper. If we're going up sustained uphill grade (ski hill) I'll pull it all out, regardless of temps.
With the grill block in place, were your coolant temp to remain above 200F for extended periods of time, I'd be worried. That 199F peak doesn't seem to be too worrisome. If you can keep the coolant below 200-210F when climbing, I don't think I'd worry about it. As soon as you start the descent, the temps will drop well below 200F.
I was thinking that the electric radiator fan doesn't even turn on until 202 or 204F. That significantly increases the cooling, usually quickly dropping the temperature below 200. If the temperature goes above that, I'll take the first stop and remove another strip or two of the blocking. If it never shows excursions below 200, I'll also remove more.
The answers on how much grill blocking is appropriate for each temp range is included in this 2009 post: 2010 Prius Grill Blocking strategy by Ken @ Japan: Celsius|Fahrenheit|lower blocking %|upper blocking % below 5|below 41|100|50 5 - 18|41 - 64|75|50 18 - 30|64 - 86|75|0 above 30|above 86|50|0 Sorry I cannot provide the link - not enough posts but you can find the thread using search
Thank you all, especiay Fuzzy1 and Cee JayNorth. After re reading the post by Cee Jay North, I realized I haven't been blocking enough. So I cut a piece of leftover pipe insulation to make an upper grill block for one side so I have the below 41f recommended block. I'll remove parts of it in the order Ken suggested but based on coolant temp as Fuzzy1 suggested.
Here's that link, with thanks to CeeJayNorth for finding it: 2010 Prius Grill Blocking strategy | PriusChat
I never had an issue with full upper block. Never removed it. Radiator has plenty of flow. I'm using A coro body kit from Japan
